1. Field of the Invention
The present invention relates to a device for production of a compound semiconductor.
2. Description of the Related Art
Examples of a method for producing a compound semiconductor include molecular beam epitaxy (hereinafter referred to as "MBE", sometimes) method, metal organic vapor phase epitaxy (hereinafter referred to as "MOVPE", sometimes) method, hydride vapor phase epitaxy (hereinafter referred to as "HVPE", sometimes) method and the like. Among them, the MOVPE method is important because there can be formed an uniform layer having a surface area larger than that of the MBE method or HVPE method.
The MOVPE method is a method of supplying precursors and carrier gas containing constituent elements of a crystal to be grown in the molecule on a heated substrate, and pyrolytically decomposing the precursors to grow the crystal on the substrate. The substrate is heated by heat transfer from a heated jig for holding the substrate, which is generally referred to as a "susceptor".
Hereinafter, the precursors together with carrier gas are referred to as raw material gas, sometimes.
The susceptor is heated by a method such as induction heating, radiative heating by resistant heater and the like. In the crystal growth by means of the MOVPE method, the growing temperature often becomes 500.degree. C. or higher and, therefore, a part whose temperature becomes high temperature such as several hundreds degrees due to radiation heating, heat transfer, etc. from the susceptor appears in the reaction vessel.
By the way, in the vapor phase epitaxy method of the compound semiconductor, the member of the device for production is exposed to a raw material gas atmosphere, such as hydrogen, metal organic compound, etc., at high temperature. Therefore, it is necessary that the member of the device for production is composed of a material which has high resistance to these raw material gases and causes little release of impurities.
Quartz is often used as a material of a member for device for semiconductor crystal growth by means of the MOVPE method because it is stable at high temperature and causes little release of impurities. However, quartz has drawbacks that the processing precision is poor and that the breakage is liable to be caused by an impact and a rapid change in temperature. Therefore, when higher processing precision and higher mechanical strength are required, a metallic material is preferably used.
On the other hand, since the metallic material having sufficient processability and sufficient mechanical strength imparts such properties, elements having an action which serves as impurities to a semiconductor material are added in almost all of cases. Therefore, when the alloy is exposed to high temperature, the alloy releases impurities contained therein and the impurities are incorporated into a crystal in the crystal growth process, thereby making it difficult to control the concentration of the impurities in the crystal or the crystal quality.